Telecommunication service providers use geographically distributed “central offices” (COs) to provide local telephone service to surrounding residential neighborhoods and businesses. As part of the service, COs also provide the electricity necessary to operate all line-powered customer equipment, primarily plain-old telephone service (POTS) telephones, within the CO service area. The electricity takes the form of direct current, or DC, power.
COs use multiple converters operating in parallel to provide the DC power. A system controller coordinates the operation of the multiple converters at each CO to ensure that they cooperate to provide the desired DC voltage and current. Since good CO design mandates converter redundancy, standby converters are almost always available to take the place of failing or failed converters. The system controller is able to detect and replace failing or failed converters with the standby converters.
As the cost of commercial power rises, the cost of operating COs rises. Telecommunication service providers therefore routinely replace older and less efficient converters at COs with newer and more efficient types. More efficient converters not only draw less AC power, they generate less heat, resulting in lower CO cooling costs. Unfortunately, converters represent a significant capital investment, so they are often replaced incrementally over a period of time as part of a long-term upgrade plan. That period of time often spans years, so today's typical CO likely contains a variety of different converter types having a range of efficiencies.